Prediction of the hardest BiFeO3 from first-principles calculations.

BiFeO3 is the only material with ferroelectric Curie temperature and Néel temperature higher than room temperature, making it one of the most well-studied multiferroic materials. Based on an ab initio evolutionary algorithm, we predicted a new cubic C-type antiferromagnetic structure (Fd3̄m-BiFeO3) at ambient pressure. It was found that Fd3̄m-BiFeO3 is the hardest BiFeO3 (Vickers hardness ∼ 9.12 GPa), about 78% harder than R3c-BiFeO3 (the well-known multiferroic material), which contributes to extending the life of BiFeO3 devices. In addition, Fd3̄m-BiFeO3 has the largest shear modulus (83.74 GPa) and the largest Young's modulus (214.72 GPa). Besides, we found an interesting phenomenon that among the common multiferroic materials (BiFeO3, BaTiO3, PbTiO3, SrRuO3, KNbO3, and BiMnO3), Pnma-BiMnO3 has the largest bulk modulus, and its bulk modulus is about 15% larger than that of Fd3̄m-BiFeO3. However, its Vickers hardness (4.47 GPa) is much smaller than that of Fd3̄m-BiFeO3. This is because the Vickers hardness is proportional to the shear modulus and the shear modulus of Fd3̄m-BiFeO3 is larger than that of Pnma-BiMnO3. This work provides a deeper and more comprehensive understanding of BiFeO3.

Synthesis of Active Hexafluoroisopropyl Benzoates via a Multicomponent Reaction.

Herein, we describe an efficient, practical free-metal rapid access to active hexafluoroisopropyl benzoates from anthranils, hexafluoroisopropanol, and N-alkoxy α-halogenoacetamides. Notably, this process includes anthranils that underwent a distinct pattern reaction. The protocol has good functional group tolerance and a broad substrate scope. Using a simple and general method, we accomplished potential synthetic application of active ester.

Sandwiched WS2/MoTe2/WS2 Heterostructure with a Completely Depleted Interlayer for a Photodetector with Outstanding Detectivity.

Photodetectors based on two-dimensional van der Waals (2D vdW) heterostructures with high detectivity and rapid response have emerged as promising candidates for next-generation imaging applications. However, the practical application of currently studied 2D vdW heterostructures faces challenges related to insufficient light absorption and inadequate separation of photocarriers. To address these challenges, we present a sandwiched WS2/MoTe2/WS2 heterostructure with a completely depleted interlayer, integrated on a mirror electrode, for a highly efficient photodetector. This well-designed structure enhances light-matter interactions while facilitating effective separation and rapid collection of photocarriers. The resulting photodetector exhibits a broadband photoresponse spanning from deep ultraviolet to near-infrared wavelengths. When operated in self-powered mode, the device demonstrates an exceptional response speed of 22/34 µs, along with an impressive detectivity of 8.27 × 1010 Jones under 635 nm illumination. Additionally, by applying a bias voltage of -1 V, the detectivity can be further increased to 1.49 × 1012 Jones, while still maintaining a rapid response speed of 180/190 µs. Leveraging these outstanding performance metrics, high-resolution visible-near-infrared light imaging has been successfully demonstrated using this device. Our findings provide valuable insights into the optimization of device architecture for diverse photoelectric applications.